Preparation and characterization of carboxymethyl derivatives of yeast mannans in aqueous solutions

Abstract

Novel carboxymethyl derivatives of yeast mannans of different degrees of substitution (DS) were prepared by optimized reaction of concentrated polysaccharides in alkaline aqueous solution. Mannans from various yeasts differing in size and degree of branching show similar reactivity. Strong alkaline conditions during carboxymethylation caused degradation of the polysaccharides. The degree of substitution (DS) of Candida albicans mannan and dextran were proportional to the amount of monochloroacetate added. However, degrees of carboxymethylation of Candida albicans mannan (0.30, 0.41, 0.73) were lower than those of dextran (DS=0.33, 0.6, 1.1) using the same amounts of monochloroacetate. Evidently the resulted polyanionic derivatives have higher hydrodynamic sizes than the original polysaccharides. Non-uniform, variable position of substitutions results to non-proportional change of optical rotation and increase of complexity of NMR spectra. Basic physico-chemical characteristics of novel carboxymethyl mannans obtained by potentiometric titration, FT-IR, UV, HPLC, 1H NMR and optical rotation measurements are presented here.

Keywords: Carboxymethylated mannans; FT-IR; NMR; Optical rotation.